1. Field of the Invention
The present invention relates to a method of culture of human cells which makes it possible to attain an efficient subculture of human somatic cells separated from an individual body for a long period of time.
2. Description of the Prior Art
It has heretofore been necessary to employ so-called subcultures of human cells for wide categories of biological studies of human beings including medicine, pharmacology and so on as an effective and practical means of conducting research. For this reason, in recent years subcultures of human cells has found application in various fields of research, such as in elucidation of the mechanism of cancer and in applications of the technique of cytofusion for the purpose of obtaining medically effective substances.
In general, for subculture of animal cells, it is necessary to use, with a few exceptions, a serum of, for example, an adult, neonate or fetus of cattle, horse, chicken, rabbit and other animal, in addition to the chemically defined synthetic culture medium consisting of amino acids, vitamins, minerals and so on. The reason for the indispensability of the serum is based on the fact that a matter that causes cell multiplicative growth (a substance other than the general nutritive materials) is contained therein, so that multiplication of cells is impossible without serum, owing to the lack of this causal matter.
It has been experienced, however, that a maximum of up to about 50-60 generation cycles is not exceeded in subcultures of normal human cells in vitro, even when cultivating such cells in a basal culture medium containing animal serum (ordinarily a cattle fetus serum). After passing this maximum number of successive generations, it has been observed either that alterations in the normal morphological aspect of the cells and in the hereditary genes were brought about, or that no further normal cell division was possible and the whole mass underwent biolysis, so that a succeeding generation cell strain has only been obtainable for a restricted number of successive generations. Therefore, renewed procurement of normal human cells has been inevitable.